1. Field of the Invention
The present invention relates to methods and equipment for assembling heat sinks and semiconductor modules.
2. Description of the Related Art
Improvements in compact semiconductor modules have played an important role in improving the performance and reducing the sizes of devices used or manufactured in many industries. For example, common central processing units (CPUs), which typically operated at about 1 MHz when first in widespread use, now typically operate processing speeds between 500 MHz and 1 GHz. Similarly, common semiconductor modules for memory systems initially had a storage capacity of about 48 Kbyte but now commonly provide a storage capacity of 1 Gbyte.
As the storage capacity of the semiconductor module designs increased, the typical access speed improved to about 8 to 10 nsec from hundreds of nanoseconds. When compared with operating speeds of information processing systems (e.g., CPUs), the processing speeds of memory systems have not increased in the same proportions. This has caused trouble in maximizing the performance of information processing systems. One attempt to solve these problems and maximize the performance of the information processing system uses a relatively fast cache memory. However, cache memories still have several drawbacks.
Lately, so-called xe2x80x9cRAMBUS DRAM(copyright)xe2x80x9d (a trademark of Rambus Corporation)xe2x80x9d has been developed to improve the performance of memories generally. The Rambus DRAM has a high efficiency of 95% and a processing speed of 1.6 nsec, which is four times processing speed of xe2x80x9cSync Link DRAM (SLDRAM) of 400 Mbyte/secxe2x80x9d otherwise known as the most rapid semiconductor module.
A semiconductor module containing memory chips operating at high speed has a weakness in that the module is susceptible to damage from external shock because of the semiconductor chips are mounted on a base plate in a flip-chip configuration to reduce the size of the semiconductor module.
Additionally, the wiring width and the wiring interval of inside signal lines of the semiconductor chips must be small to obtain a high level of integration and rapid processing speed. The narrow wiring width increases the internal intrinsic resistance, so that operation of the memory chips generates lots of heat. Therefore, in general, semiconductor products operating at high speed must rapidly radiate heat to prevent degradation of performance or damage to the products. To protect the semiconductor chips and achieve the necessary heat radiation from a semiconductor module operating at high speed, heat sinks, which have a prescribed strength and a high thermal conductivity, are mounted, for example, riveted on the semiconductor module. The heat sink must be mounted on or surrounding the semiconductor chips of the semiconductor module and commonly use materials such as an aluminum alloy that has a high thermal conductivity. After a rivet protruding is inserted through aligned holes in a printed circuit board and the heat sink, a punch deforms the rivet to stably combine the printed circuit board and the heat sink.
Some embodiments of the present invention provide methods and automated equipment for assembling heat sinks on semiconductor modules. One embodiment of the equipment includes a plurality of built-up pads that receive heat sinks and semiconductor modules while from station to station around a loop. The equipment rivets the heat sinks and the semiconductor modules together using a rivet that was provided in a first heat sink on a built-up pad. At a last station on the loop, the equipment inspects the rivets and a label to determine whether the finished semiconductor module is good or bad.
In one exemplary embodiment of the present invention, the equipment comprises: a base body; a built-up pad conveying unit; a first heat sink supply unit; a semiconductor module unloading unit; a second heat sink supply unit; a riveting unit; a semiconductor product loading unit; and a tray conveying unit. The built-up pad conveying unit is mounted at the upper center of the base body and contains a plurality of built-up pads for assembly of heat sinks and semiconductor modules. The first heat sink supply unit seats the first heat sink, in which a rivet is mounted, on one of the built-up pads. The semiconductor module unloading unit seats the semiconductor module from a tray, on the first heat sink on the built-up pad, with the rivet of the first heat sink through a matching hole in the semiconductor module. The second heat sink supply unit seats a second heat sink onto the semiconductor module with the rivet inserted through a hole in the second heat sink, after the built-up pad with the combined first heat sink and semiconductor module is transferred one step. The riveting unit works an end of the rivet to rivet the first heat sink, the semiconductor module, and the second heat sink together after the built-up pad is transferred another step. After the riveting, the semiconductor product loading unit loads the semiconductor products on the tray. The tray conveying unit transfers trays from the semiconductor module unloading unit to the semiconductor product loading unit.
Another embodiment of the present invention, is a method for assembling heat sink to semiconductor module. The method comprises: seating a first heat sink, on which a rivet is mounted, on a built-up pad of a built-up pad conveying unit and transferring the built-up pad one step; seating a semiconductor module transferred from a tray onto the first heat sink with the rivet through a hole in the semiconductor module and transferring the built-up pad another step; seating a second heat sink on the semiconductor module with the rivet through a hole in the second heat sink and transferring the built-up pad another step; deforming the rivet to attach and fix the semiconductor module and the heat sinks and transferring the built-up pad another step; and unloading the semiconductor modules from the built-up pad, onto an empty tray after unloading all of the semiconductor modules from the tray.